First Indian Aquanauts Reach 5,000 Metres Depth and Hoist National Flag

India marks a historic milestone in ocean exploration as aquanauts descend 5,000 metres in the Atlantic Ocean and hoist the national flag, paving the way for the Samudrayaan Mission and future deep-sea expeditions.

In a historic scientific milestone, Indian aquanauts successfully descended to a depth of 5,000 metres below sea level in the Atlantic Ocean, marking a new era in India’s deep-sea exploration capabilities. This achievement occurred just weeks after India recorded its first human presence on the International Space Station (ISS), showcasing the country's parallel advancements in space and ocean science.

On August 5 and 6, 2025, two Indian aquanauts — Raju Ramesh, Senior Scientist at the National Institute of Ocean Technology (NIOT), and Commander (Retd.) Jatinder Pal Singh, formerly of the Indian Navy — carried out deep-sea dives in the French submersible “Nautile”, operated by the French marine research institute IFREMER.

Ramesh reached a depth of 4,025 metres on August 5, followed by Singh, who descended to 5,002 metres on August 6. Each dive lasted approximately seven hours, and both individuals returned safely to the surface.

Hoisting the National Flag during the Indian Aquanauts 5000 Metres Dive

As part of this groundbreaking expedition, the Indian national flag (Tiranga) was planted at the ocean floor, symbolizing India’s commitment to oceanic research and scientific sovereignty. This was the first time India had marked its presence at such depths beneath the sea, a milestone comparable to its achievements in outer space.

What is the Deep Ocean Mission (DOM)?

Launched in 2021 and implemented by the Ministry of Earth Sciences, the Deep Ocean Mission (DOM) is a multi-disciplinary initiative aimed at exploring and harnessing deep-sea resources, including:

• Crewed and uncrewed submersibles

• Deep-sea mining technologies

• Ocean climate services

• Marine biodiversity research

• Ocean-based renewable energy systems

One key component is the Samudrayaan Mission, which involves deploying a crewed submersible to depths of up to 6,000 metres to explore India’s Exclusive Economic Zone (EEZ) and continental shelf. The term “Samudrayaan” is derived from Sanskrit, meaning “sea journey”.

India’s Indigenous Submersible MATSYA-6000: The Next Phase After the 5000 Metres Dive

The flagship development under the DOM is MATSYA-6000, a fourth-generation, crewed deep-sea submersible designed to carry three people to a depth of 6,000 metres. It houses its crew inside a 2.1-metre-diameter titanium alloy sphere, capable of withstanding 600 times atmospheric pressure.

Key Features of MATSYA-6000:

• Scientific sensors

• Data and voice communication systems

• Emergency safety subsystems

• High-density Li-Po battery

• Drop-weight emergency escape system

• Underwater acoustic telephone

• Emergency endurance of up to 96 hours (normal mission duration: 12 hours)

• Bio-vests for crew safety and health monitoring

The submersible successfully completed wet trials at L&T Shipyard, Kattupalli, Tamil Nadu in January–February 2025. It is expected to undergo 500-metre shallow water trials by early 2026, followed by deep-sea testing and deployment by 2027.

The Indo-French Collaboration and Training Expedition

The recent expedition was conducted in collaboration with IFREMER of France, utilizing the submersible Nautile. A five-member team from NIOT participated in the mission to gain hands-on experience prior to deploying India’s own submersible.

The NIOT team, which boarded IFREMER’s research vessel L’Atalante off the coast of Lisbon, Portugal on August 3, 2025, included:

• Dr. Ramesh Sethuraman (Team Leader, Scientist G & Group Head for MATSYA-6000)

• Sh. Palaniappan

• Dr. D. Sathianarayanan

• Sh. G. Harikrishnan

Training and Operational Tasks Completed:

• Pre-dive preparation and submersible piloting

• Descent and ascent protocols

• Buoyancy control

• Use of manipulator arms for flag planting and sample collection

• Deployment and recovery of the submersible

• Acoustic communication between sub and ship

• Trajectory tracking and dive planning

These exercises provided critical insights into the operational challenges and system requirements for future Indian missions.

Roadmap for MATSYA-6000 and Future Missions

The knowledge gained from the current expedition will directly contribute to finalizing MATSYA-6000’s development, integration, and testing. The roadmap includes:

• Completion and testing of titanium hull, syntactic foam (for buoyancy), Variable Ballast System (VBS), and drop-weight safety mechanisms

• Open ocean certification of all systems

• 500-metre demonstration dives in 2026

• Research vessel augmentation with Launch and Recovery System (LARS)

• Integration and full-depth testing by mid-2027

• Commencement of scientific missions by 2027–28

Upon completion, India will become the sixth country globally to develop and deploy a manned deep-sea submersible, joining the ranks of the USA, Russia, France, China, and Japan.

Harnessing India’s Ocean Wealth and Blue Economy

With a coastline of 11,098 km and a vast Exclusive Economic Zone (EEZ), India has significant untapped marine potential. The DOM is aligned with national efforts to expand the blue economy—a strategy that emphasizes the sustainable use of ocean resources for economic growth, improved livelihoods, and environmental health.

India has also signed a contract with the International Seabed Authority (ISA) to explore polymetallic nodule-rich regions at depths between 4,000 and 5,500 metres. These nodules contain essential minerals such as nickel, cobalt, manganese, and copper, critical for energy storage and advanced manufacturing technologies.

Historical Context

While Indian scientists had previously participated in deep-sea dives using foreign submersibles—reaching 3,800 metres in Alvin (USA, 1997) and 2,800 metres in Nautile (France, 2002)—the recent dives in 2025 set a new national record and represent India's first independent manned deep-sea achievements.